Touch device

ABSTRACT

An assembly for holding and controlling curvature of a glass plate for an optical touch sensitive system is described. The assembly comprising a first frame element extending in a first plane and configured to extend at least partially around a panel; at least one second frame element extending in a second plane and forming a support portion for the plate, and at least one spacing element positioned at least partially between the support portion and the first frame element. The spacing element us configured to control a curvature of the first frame element and wherein the at least one second frame element is configured to engage the plate at the support portion, is attached to the first frame element, and is tiltable, by controlling the curvature of the first frame element with said spacing element, to control a curvature of the plate.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57.

BACKGROUND Field of the Invention

This invention relates in general to the field of optical touchsensitive systems. More particularly, the invention relates to a curvedplate and an assembly for holding a plate of the system, such as a glassplate, relative to a panel such that curvature of the plate iscontrolled. The invention also relates to a method for assembling aplate of an optical touch sensitive system with a panel (such as adisplay panel) in such a way that curvature is controlled.

Background of the Invention

In one category of touch sensitive panels known as above surface opticaltouch systems and known from e.g. U.S. Pat. No. 4,459,476, a pluralityof optical emitters and optical receivers are arranged around theperiphery of a touch surface to create a grid of intersecting lightpaths above the touch surface. Each light path extends between arespective emitter/receiver pair. An object that touches the touchsurface will block certain ones of the light paths. Based on theidentity of the receivers detecting a blocked light path, a processorcan determine the location of the intercept between the blocked lightpaths. This type of system is only capable of reliably detecting thelocation of one object (single-touch detection). Further, the requirednumber of emitters and receivers, and thus cost and complexity,increases rapidly with increasing surface area and/or spatial resolutionof the touch panel.

In a variant, e.g. shown in WO2006/095320, each optical emitter emits abeam of light that diverges across the touch surface, and each beam isdetected by more than one optical receiver positioned around theperiphery of the touch surface.

These systems typically direct light to travel across the surface of thetouch surface at a height of up to 5 mm.

Other above surface touch sensitive systems use tomographic touchimaging for sensing a touch, e.g. as described in WO2016/130074. Suchsystems allow for directing the light much closer to the touch surface,which in turn allows for significant improvements in accuracy andrequires a lower light budget. The light is typically directed at aheight of up to about 1 mm above the plate.

Typically, the touch surface is a glass plate. In systems where thelight is directed closer to the touch surface, distortions in the platehave a disproportionally large effect on the light signal. Therefore,glass plates as used in previously known above surface optical touchsystems are unsuitable when the light is transmitted closer to theplate, since the accuracy of the system is impaired by the distortionsin the plate.

Additionally, a frame for assembly of the plate of the optical touchsensitive system and a panel, such as an LCD panel, may introducedistortion in the form of uncontrolled warpage, i.e. a twist or curve inthe plate is introduced even if it is usually flat. The uncontrolledwarpage may even block the light transmitted across the plate. This isdue to uncontrolled twisting of the frame as such when it is attached tothe panel.

Although not described in relation to touch systems, methods ofminimizing glass warpage are known from the window industry and from thedisplay panel industry. Such solutions include pre-bent glass in orderto control warpage. However, such solutions are unsuitable/insufficientfor touch sensitive systems since they typically require bulky frames atthe border of the glass and/or pressure points closer to the center ofthe panel where force may be applied to control the shape of the glass.These solutions are unsuitable where a minimal/lightweight border bezelis required, and no supporting objects may touch the glass further inthan at the borders. Additionally, pre-bent glass is expensive andfragile to transport.

Therefore, an improved frame assembly for holding a plate of an opticaltouch sensitive system relative to a panel would be advantageous and inparticular allowing for improved precision, increased compactness,cost-effectiveness, and/or controlled curvature would be advantageous.Further, a touch panel having a shape conducive to transmitting as muchlight from the emitters as possible to the detectors is needed.

SUMMARY OF THE INVENTION

Accordingly, embodiments of the present invention preferably seek tomitigate, alleviate or eliminate one or more deficiencies, disadvantagesor issues in the art, such as the above-identified, singly or in anycombination by providing an assembly, a method for assembling, and a kitof frame elements according to the appended patent claims.

A first embodiment of the invention describes an assembly for holdingand controlling curvature of a plate for an optical touch sensitivesystem, comprising a first frame element extending in a first plane andconfigured to extend at least partially around a panel; at least onesecond frame element extending in a second plane and forming a supportportion for the plate, and at least one spacing element positioned atleast partially between the support portion and the first frame element,the spacing element being configured to control a curvature of the firstframe element, and wherein the at least one second frame element isconfigured to engage the plate at the support portion, is attached tothe first frame element, and wherein the shape and/or position of thesecond frame element is controlled by the curvature of the first frameelement with said spacing element, to control a curvature of the plate.

A second embodiment of the invention describes a method for assembling apanel and a plate for an optical touch sensitive system, comprising:providing a first frame element extending in a first plane andconfigured to extend at least partially around a panel; providing atleast one second frame element forming a support portion for the plate;supporting the plate by the support portion; attaching the second frameelement to the first frame element such that the support portion extendsat least partially in a second plane generally opposite at least aportion of the first frame element and is spaced apart from the firstplane; and controlling a curvature of the first frame element with aspacing element attached to the first frame element and thereby tiltingthe support portion to control a curvature of the plate.

A third embodiment of the invention describes a kit of frame elementsfor assembling a panel and a plate for a touch sensitive system,comprising: a first frame element extending in a first plane; at leastone second frame element forming a support portion for the plate andbeing attachable to the first frame element, and a spacing elementadjustably attachable to the first frame element; wherein at least aportion of the support portion is tiltable, by the spacing element,relative to the first frame element to extend in the second plane, whichis curved.

Some embodiments of the invention provide for controlling curvature of aplate for an optical touch sensitive system such that it does not occurwhen the plate is assembled with a panel. This prevents distortion inthe plate from affecting a light signal transmitted across the plate,which in turn allows improvements in accuracy and lower light budget ofthe system. Additionally, or alternatively, embodiments provide forcontrolling curvature such that the field of view, for a detectorreceiving light from a light emitter of the touch sensitive system, isincreased compared to a substantially flat plate. Again, the improvedfield of view provides for improved accuracy of the touch sensitivesystem and allows for a better light budget. Furthermore, embodimentsprovide for an assembly that is compact at the same time as curvaturemay be controlled. Also, the curvature may be controlled withoutcontacting the center of the plate.

A fourth embodiment of the invention describes a touch sensingapparatus, comprising a touch surface; a set of emitters arranged aroundthe touch surface to emit first beams of light to propagate across thetouch surface, a set of light detectors arranged around the touchsurface to receive light from the first set of emitters, wherein eachlight detector is arranged to receive light from more than one emitter;a processing element configured to determine, based on output signals ofthe set of light detectors, the position of an object on the touchsurface, wherein the touch surface is curved in a first axis accordingto a first parabola.

It should be emphasized that the term “comprises/comprising” when usedin this specification is taken to specify the presence of statedfeatures, integers, steps or components but does not preclude thepresence or addition of one or more other features, integers, steps,components or groups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of which embodiments ofthe invention are capable of will be apparent and elucidated from thefollowing description of embodiments of the present invention, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a top view of the first frame element showing cross-sectionalaxes A-A and B-B;

FIGS. 2a-2d are cross-sectional views of embodiments of assemblies;

FIG. 3a is a schematic illustration showing the cross-section axis B-Bof FIG. 1 of the assembly with the second frame element relative to thefirst frame element and holding the plate in a flat plane;

FIG. 3b is a schematic illustration showing the cross-section axis A-Aof FIG. 1 of the assembly with the second frame element relative to thefirst frame element and holding the plate in a flat plane;

FIG. 3c is a schematic view (cross section) showing the cross-sectionaxis B-B of FIG. 1 of the assembly with the second frame element warpedrelative to the first frame element and holding the plate in a curvedplane that is concave;

FIG. 3d is a schematic view (cross section) showing the cross-sectionaxis A-A of FIG. 1 of the assembly with the second frame element warpedrelative to the first frame element and holding the plate in a curvedplane that is concave;

FIG. 4a is a perspective view of the first frame element;

FIG. 4b is a schematic illustration of the panel in a convex shape andthe frame of the first frame element in a concave shape, including plate2 also controlled into a concave shape;

FIG. 4c is a side view showing screws 116 a and 116 b;

FIGS. 5a-5h are side views and perspective views of an embodiment of theassembly comprising a screw arrangement for configuring frame shape; and

FIG. 6 is a schematic cross section from a first direction of anembodiment of the assembly;

FIG. 7 is a schematic side-view of another embodiment for providingcurvature of plate 2;

FIG. 8 shows an isometric view of a variation of the embodiment of FIGS.5a -5 g;

FIG. 9 is a diagram showing a top down view of an optical touch systemand corresponding detection lines;

FIG. 10a shows an isometric view of a flat touch surface of an opticaltouch system;

FIG. 10b shows a section view of an optical touch system with a flattouch surface;

FIG. 11a shows an isometric view of a touch surface of an optical touchsystem having a curved profile in the x-axis;

FIG. 11b shows a section view along the x-axis of an optical touchsystem with a touch surface having a curved profile in the x-axis;

FIG. 11c shows a section view along the x-axis of an optical touchsystem with a touch surface having a curved profile in the x-axis;

FIG. 11d shows an example of types of warpage that a touch panel mayexhibit.

FIG. 12a shows top view of a touch surface of an optical touch system;

FIG. 12b shows an isometric view of a touch surface of an optical touchsystem having a curved profile in the x-axis and a curved profile in they-axis;

FIG. 12c shows a section view along the x-axis of an optical touchsystem with a touch surface having a curved profile in the x-axis and acurved profile in the y-axis;

FIG. 12d shows a section view along the y-axis of an optical touchsystem with a touch surface having a curved profile in the x-axis and acurved profile in the y-axis;

FIG. 13a shows a section render of light emitted from a point at an edgeof a curved touch surface and propagating across the curved touchsurface to be received at a detector at an opposite edge of the touchsurface;

FIG. 13b shows a graph of light emitted from a point at an edge of acurved touch surface and received at a detector at an opposite edge ofthe touch surface with respect to the angle of the emitter light;

FIG. 14a shows a section render of light emitted from a point at an edgeof a curved touch surface and propagating across the curved touchsurface to be received at a detector at an opposite edge of the touchsurface;

FIG. 14b shows a graph of light emitted from a point at an edge of acurved touch surface and received at a detector at an opposite edge ofthe touch surface with respect to the angle of the emitter light;

FIG. 15a shows a section render of light emitted from a point at an edgeof a curved touch surface and propagating across the curved touchsurface to be received at a detector at an opposite edge of the touchsurface;

FIG. 15b shows a graph of light emitted from a point at an edge of acurved touch surface and received at a detector at an opposite edge ofthe touch surface with respect to the angle of the emitter light;

FIG. 16a shows a section render of light emitted from a point at an edgeof a curved touch surface and propagating across the curved touchsurface to be received at a detector at an opposite edge of the touchsurface;

FIG. 16b shows a graph of light emitted from a point at an edge of acurved touch surface and received at a detector at an opposite edge ofthe touch surface with respect to the angle of the emitter light;

FIG. 17a shows a section render of light emitted from a point at an edgeof a curved touch surface and propagating across the curved touchsurface to be received at a detector at an opposite edge of the touchsurface;

FIG. 17b shows a graph of light emitted from a point at an edge of acurved touch surface and received at a detector at an opposite edge ofthe touch surface with respect to the angle of the emitter light;

FIG. 18a shows a curvature of a real touch surface vs a parabolic curvedsurface along an x-axis;

FIG. 18b shows a deviation between a real touch surface vs a paraboliccurved surface along an x-axis;

FIG. 19a shows a curvature of a real touch surface vs a parabolic curvedsurface along an x-axis;

FIG. 19b shows a deviation between a real touch surface vs a paraboliccurved surface along an x-axis;

FIG. 20a shows top view of displacement contours for a touch surfaceaccording to an embodiment;

FIG. 20b shows curvature of a touch surface along an x-axis according tothe embodiment of FIG. 20 a;

FIG. 20c shows curvature of a touch surface along a y-axis according tothe embodiment of FIG. 20 a;

FIG. 20d shows curvature of a touch surface along a diagonal lineaccording to the embodiment of FIG. 20 a;

FIG. 21a shows top view of displacement contours for a touch surfaceaccording to another embodiment;

FIG. 21b shows curvature of a touch surface along an x-axis lineaccording to the embodiment of FIG. 21 a;

FIG. 21c shows curvature of a touch surface along a y-axis lineaccording to the embodiment of FIG. 21 a;

FIG. 21d shows curvature of a touch surface along a diagonal lineaccording to the embodiment of FIG. 21 a.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Specific embodiments of the invention will now be described withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Theterminology used in the detailed description of the embodimentsillustrated in the accompanying drawings is not intended to be limitingof the invention. In the drawings, like numbers refer to like elements.

In optical touch sensitive systems, a plate 2 of the system, such as aglass plate may be arranged opposite a panel 1, such as an LCD panel oradditional frame. The plate 2 is normally substantially flat. Theperimeter of the plate 2 after integration is a concern: the foursides/edges of the plate 2 must all be plane or slightly concave as seenfrom the touch surface, i.e. the side of the plate 2 above which lightis transmitted. An aspect of this is to ensure that the mechanical partsthat hold or support the perimeter of the plate 2 are free fromconvexity. Sometimes, there are several components that are involved inholding the plate 2 (back cover, carriers, edge cover, screw bossesetc.) The stiffer component of the assembly, the more it will govern thefinal shape of the plate 2.

In prior art solutions, the frame that holds the plate 2 at theedge/perimeter may introduce some twist (the corners will not layperfectly on a flat plane) to the plate. Twist may induce convexityalong the plate diagonals and should thus be minimized or avoided. Thetwist tolerance depends, e.g., on glass specification, product, size,shape of integrated glass perimeter, and on how a VESA mount isattached.

FIG. 1 shows an embodiment of a frame assembly 100, 200 that preventsinducement of convexity along the plate, such as along the plate edgesand/or diagonals. Some embodiments avoid convexity and may even induceconcavity to further improve the touch system. Frame 109 is formed fromfirst frame element 102. Attachment element 112 and spacing element 116are described in the embodiments below.

According to some embodiments of the invention, an assembly 100, 200,which is configured to hold or support the plate 2 and the panel 1,applies a controlled force to the plate 2 such that curvature of theplate 2 is controlled. In the embodiments illustrated in FIGS. 2a-2c and3a-3d , the force applies a torque to a support portion 101 a, 101 b forthe plate 2. In the embodiments of FIGS. 4a-4c , the force issubstantially straight and perpendicular to the plate 2. In thefollowing, the embodiments of FIGS. 2a-2c, 3a-3d, 4a-4c , and 5 a-5 gwill be described separately. However, these embodiments may be combinedto provide further embodiments, such as the combination illustrated inFIGS. 6a -6 c.

FIGS. 2a-2d illustrate embodiments wherein the frame assembly 100comprises a first frame element 102 and at least one second frameelement 103 a, 103 b. The first frame element 102 may form a rearbracket frame that extends at least partially over the backside of thepanel 1. The second frame element 103 a, 103 b may form a holder orsupport bracket. Furthermore, second frame element 103 a, 103 b mayextend along at least a portion of a perimeter of the plate 2 and/or thepanel 1. Separate second frame elements 103 a, 103 b may extend at leastpartially along the perimeter of different sides of the plate 2 and/orpanel 1. For example, two second frame elements 103 a, 103 b may extendalong opposing perimeters of the plate 2 and/or panel 1. Alternatively,four second frame elements 103 a, 103 b may extend along the perimeterof the plate 2 and/or panel 1, i.e. one along each side of a rectangularplate 2 and/or panel 1.

As is illustrated in FIGS. 4a-4c , the panel 1 may be held between thefirst frame element 102 and the second frame element 103 a, 103 b. Theplate 2 may be supported or held at a first side of a portion of thesecond frame element 103 a, 103 b forming the support portion 101 a, 101b. The panel 1 may be held or supported by a second side of the supportportion 101 a, 101 b, which forms a support portion for the panel 1. Anadhesive 104, such as an adhesive tape, may be arranged between thesupport portion 101 a, 101 b and the plate 2. A gasket 105 may bearranged between the support portion 101 a, 101 b and the panel 1.

In one embodiment, elements 102, 103 (shown in the figure as comprisingelements 103 a and 103 b) are formed from a single piece.

The second frame element 103 a, 103 b may be attached to the first frameelement 102.

In the embodiments of FIGS. 2a-2c and 3a-3d , the second frame element103 a, 103 b, is attached to the first frame element 102 by at least oneattachment member 106 a, 106 b, such as a screw, a weld, a rivet etc.Therefore, the second frame element 103 a, 103 b may be rigidly attachedto the first frame element 102.

The first frame element 102 may comprise a flange 107 a, 107 b thatextends at the perimeter of the first frame element 102. Similarly, thesecond frame element 103 a, 103 b may comprise a flange 108 a, 108 b.When assembled, the flange 107 a, 107 b of the first frame element 102may be arranged in abutment with the flange 108 a, 108 b of the secondframe element 103 a, 103 b. The flange 107 a, 107 b of the first frameelement 102 may be held together with the flange 108 a, 108 b of thesecond frame element 103 a, 103 b by the attachment member 106 a, 106 b.

The first frame element 102 may form a frame 109 (shown in FIG. 1) thatextends in a first plane. The frame 109 is configured to extend at leastpartially around a first side of a panel 1. The first side of the panel1 may be the backside of the panel 1. In some embodiments, the frame 109has a width, such as 3-10 cm. The frame 109 may extend from the edges ofthe first side towards the center of the first side of the panel 1.Therefore, the frame 109 may be rectangular, and made from a singlepiece of material.

As is illustrated in FIGS. 3a and 3b , the assembly 100 may comprise atleast one support area 110 a, 110 b for supporting a back cover 111. Thesupport area 110 a, 110 b may extend in a plane that is substantiallyparallel to the first plane, in which the frame 109 extends. The supportarea 110 a, 110 b may be located further away from the support portion101 a, 101 b of the second frame element 103 a, 103 b than the frame109, such that the frame 109 and the back cover 111 are spaced apart. Inthe illustrated embodiment, the support area 110 a, 110 b is providedbetween the flange 107 a, 107 b and the frame 109 of the first frameelement 102. The back cover 111 may be attached to the support area 110a, 110 b, e.g. by attachment elements, such as screws.

In other embodiments, the support area 110 a, 110 b is provided by theflange 108 a, 108 b of the second frame element 103 a, 103 b. The flange107 a, 107 b of the first frame element 102 may be connected to thesecond frame element 103 a, 103 b between the flange 108 a, 108 b andthe support portion 101 a, 101 b of the second frame element 103 a, 103b.

The second frame element 103 a, 103 b may form the support portion 101a, 101 b. For example, the second frame element 103 a, 103 b may form anelongated member that is at least partly L-shaped in cross-section. Whenassembled, the second frame element 103 a, 103 b may extend along theperimeter of the panel 1, and wrap around the perimeter of the panelsuch that the support portion 101 a, 101 b extends at least partially ina second plane generally opposite the frame 109 and spaced apart fromthe first plane. Thereby the second frame element 103 a, 103 b isconfigured to extend at least partially at a second side of the panel 1,e.g. at a front side of the panel 1.

In some embodiments, the second frame element 103 a, 103 b has a firstportion and a second portion. The first portion may be provided at anangle relative to the second portion. The second portion may form thesupport portion 101 a, 101 b and be configured to extend in the secondplane opposite the frame 109. The first portion may extend between thesecond portion and the first frame element 102. Also, the first portionmay extend along the edge or side surface of the plate 2 when assembled.The first frame element 102 may be connected to the first portion of thesecond frame element 103 a, 103 b. The first portion may besubstantially perpendicular to the second portion.

As is illustrated in FIGS. 3a-3d , the first frame element 102 may beattached to the first portion of the second frame element 103 a, 103 bsuch they are fixed relative to each other. Furthermore, the secondframe element 103 is tiltable relative to the first frame element 102. Aforce applied to the first frame element 102 is transferred to thesecond frame element 103 such that the support portion 101 a, 101 b istilted towards the first frame element 102. Thus, a torque may controltilt of the second portion of the second frame element 103 a, 103 b,i.e. the support portion 101 a, 101 b that supports the plate 2,relative to the first frame element 102, which is illustrated with acurved arrow in FIGS. 3c and 3d . In some embodiments, the angle of tiltof the support portion 101 a, 101 b is controlled to be neutral, i.e.the angle of tilt of the support portion 101 a, 101 b is controlled suchthat it is substantially parallel with the panel 1 and/or controls theplate 2 to be in a flat plane, as is illustrated in FIGS. 3a and 3b . Inother embodiments, the angle of tilt of the support portion 101 a, 101 bis controlled to be negative relative to the touch surface, i.e. theangle of tilt of the support portion 101 a, 101 b is controlled suchthat the free end of the support portion 101 a, 101 b is tilted towardsthe frame 109, as is illustrated in FIGS. 3c and 3d . In the lattercase, the plate 2 is given a slightly concave shape, i.e. in thedirection from the touch surface of the plate 2 towards the panel 1. Ineach of these cases curvature is controlled such that the field of view,for a detector receiving light from a light emitter of the touchsensitive system, is improved since convexity in the plate is avoided.Again, improved field of view provides for improved accuracy of thetouch sensitive system and allows for lower light budget. Furthermore,since the support portion 101 a, 101 b only needs to extend a shortdistance over the plate 2 at the perimeter the assembly is compact atthe same time as curvature may be controlled. Also, curvature may becontrolled without contacting the center of the plate. When theconcavity is applied, the sensitivity of the system may be even furtherimproved.

FIGS. 2a-2d and 3a-3d illustrate embodiments of an attachment element112 for attaching the first frame element 102 to the panel. A pluralityof attachment elements 112 (e.g. as shown in triplicate as elements 112a, 112 b, and 112 c) may be arranged around the frame 109, such as ateach corner of the frame 109, which is illustrated as circles in FIG. 4a. Each attachment element may comprise a group of screws 112 a, 112 b,112 c, 113 a, 113 b. Each screw may be arranged in a hole of the frame109, which may be threaded. Each attachment element may comprise atleast two screws 112 a, 112 b, 112 c, 113 a, 113 b. At least one of thescrews 112 a, 113 a may be arranged to displace the frame 109 away frompanel 1, which is indicated with an arrow in FIG. 2d e.g. by having athread in the frame 109 and pushing on the panel 1. At least one otherof the screws 112 b, 112 c, 113 b may be arranged to displace the frame109 towards the panel 1, which is also indicated with an arrow in FIG.2d . e.g. by having a thread in the panel and a hole in frame 109.

FIG. 2a illustrates an embodiment wherein each attachment elementcomprises at least three screws 112 a, 112 b, 112 c. All three screws112 a, 112 b, 112 c are arranged closer to a center of the first frameelement 102 than a perimeter of the support portion 101 a, 101 b, i.e.an imaginary extension 114 a, 114 b, 114 c of the longitudinal axis ofeach screw 112 a, 112 b, 112 c passes outside the support portion 101 a,101 b when viewed in cross-section, as is illustrated in FIG. 2a . Inthe illustrated embodiment, a first screw 112 a is arranged between asecond screw 112 b and a third screw 112 c. FIG. 2a only illustrates onegroup of screws. However, a group of screws may be arranged at anylocation around the frame 109 to attach the first frame element 102 tothe panel 1.

FIG. 2b illustrates an embodiment wherein each group of screws consistsof only two screws 113 a, 113 b. A first screw 113 a is arrangedopposing the support portion 101 a, 101 b, i.e. an imaginary extension115 a of the longitudinal axis of the first screw 113 a passes throughthe support portion 101 b when viewed in cross-section, such as throughthe center thereof, as is illustrated in FIG. 2b . A second screw 113 bof the two screws is arranged closer to a center of the first frameelement 102 than a perimeter of the support portion 101 b, i.e. animaginary extension 115 b of the longitudinal axis of the first screw113 b passes outside the support portion 101 b when viewed incross-section, as is illustrated in FIG. 2 b.

As shown in FIG. 2d , the first screw 112 a is arranged to displace theframe 109 away from panel 1. This may be enabled by a threaded hole 112i in the frame 102 which the first screw engages while a head of thescrew abuts the panel 1. The second screw 112 b is arranged to displacethe frame 109 towards the panel. This may be enabled by a threaded hole112 f in the panel 1, which the second screw 112 b engages while thehead of the second screw 112 b abuts the surface of the frame. By usingscrew 112 a and/or 112 b, forces may be applied to frame 102 and/orpanel 2 to control bending or rotation of the frame/panel.

Since the first screw 113 b is aligned over the support portion 101 a,101 b in the embodiment of FIG. 2b , only two screws are required tocontrol bending or rotation of the frame.

In FIGS. 2a-2b , only one group of screws is illustrated. However, agroup of screws may be arranged at any location around the frame 109 tosupport the plate 2 and the panel 1.

FIG. 2c illustrates that a combination the embodiment of FIGS. 2a and 2b, i.e. groups of screws with two as well as three screws may be arrangedaround the frame 109. Therefore, flexibility is provided for.

As is illustrated in FIGS. 2a-2c and 3c and 3d , each group of screws112 a, 112 b, 112 c, 113 a, 113 b may apply a force to the frame 109.Therefore, a torque may be applied at the second frame element 103 a,103 b via controlling the curvature of the frame 109 such that tilt ofthe support portion 101 a, 101 b, and thereby curvature of the plate, iscontrolled. In the assembly illustrated in FIG. 3a , a net force isapplied such that the frame is substantially flat and parallel with thepanel 1. In the assembly illustrated in FIGS. 3c and 3d , a net forceaway from the support portion 101 a, 101 b is provided to the frame 109,which will be slightly concave when viewed from the touch surface of theplate 2. As a consequence, a torque will be provided at to the secondframe element 103 a, 103 b, which will tilt the support portion 101 a,101 b along the edge or perimeter of the plate 2. Therefore, controllingthe curvature of the first frame element 109 may control curvature ofthe plate. The plate 2 may become concave as viewed from the touchsurface of the plate 2.

FIGS. 4a-4c, 5a-5g and 6a-6c illustrate embodiments wherein analternative or additional control of the shape of the frame 109 may beintroduced. As shown in FIG. 4a , attachment elements 112 may bearranged at the corners of the frame 109. The attachment elements 112may comprise the group of screws 112 a, 112 b, 112 c, 113 a, 113 b asdescribed above with regard to FIGS. 2a-2c and 3a-3d . The attachmentelements 112 may be arranged to pull the panel 1 towards the frame 109.This may be done with or without tilting the support portion 101 a, 101b as described above. At least one spacing element 116 (where spacingelement 116 may comprise screw 112 and a separate spacing component) maybe arranged along the perimeter of the frame 109 between two attachmentelements 112. The spacing element 116 is arranged in the assembly toapply a force to the frame 109 directed away from the panel 1. Thereby,a force applied by the spacing element 112 may be transferred to thesecond frame element 103 a, 103 b such that the support 101 a, 101 b istilted as described above, whereby curvature of the plate 2 iscontrolled.

As is illustrated in FIG. 4b , the general shape of the frame 109 willbe concave, whereas the general shape of the panel 1 may be convex. Thepanel may also remain substantially plane depending on its rigidity. Theresulting shape of the plate 2 will be concave. Therefore, each side ofthe frame 109 may be controlled to follow a curved path. The curvaturemay be controlled by adjusting the force applied by each spacing element116 and/or via the number of spacing elements 116 along each side of theframe 109. As a result, the support portion 101 a, 101 b, at least atthe free end of the support portion 101 a, 101 b, may also follow acurved path. Therefore, at least a portion of the support portion 101 a,101 b may extend in a plane that is curved.

When the second frame element 103 a, 103 b is disassembled or onlyattached to the first frame element 102, it may have a relaxed state. Inthe relaxed state, the support portion 101 a, 101 b extends in a planethat is substantially flat. The second frame element 103 a, 103 b may bedeflectable from the relaxed state to a deflected state or stressedstate, such as by the attachment elements 112 and spacing elements 116.The level of tilt at the opposing ends of the support 101 a, 101 b wherethe attachment elements 112 are provided may be less than the level oftilt between the ends where spacing element(s) 116 is/are provided. Asconsequence, the second frame element 103 a, 103 b may be deflected tothe deflected or stressed state. In the deflected or stressed state, thesupport portion 101 a, 101 b extends, along its length, in a plane thatis curved. A cross section of this plane taken along the support portion101 a, 101 b, such as at the free end or tip of the support portion 101a, 101 b may form a parabolic concave curve along at least a portion ofthe length of the support portion 101 a, 101 b. A combination of theattachment element 112 and the spacing element 116, that together mayform a screw arrangement, may hold the second frame element 103 a, 103 bin the deflected or stressed state when assembled with the first frameelement 102.

The spacing element 116 may be provided by a single screw that engages athread in the frame 109 while its tip engages or abuts a surface onpanel 1. Alternatively, panel 1 comprises a threaded hole into whichspacing element 116 is threaded so that spacing element 116 can be usedto displace the frame 109 towards panel 11. Additionally, element 116may comprise a spacer component such as a washer, spacer, etc. In FIGS.3a and 3b and FIG. 6a , two spacing elements 116 a, 116 b are shown forillustrative purposes and may form separate embodiments. Asingle-spacing element 116 a, 116 b may be used in other embodiments.The head of the spacing element 116 a, 116 b may abut the back cover 111while the spacing element 116 a, 116 b may engage the frame 109, whereinthe frame 109 may be pulled towards the back cover 111. As a result, theframe 109 becomes concave. In some embodiments, the spacing element 116a does not abut or engage the panel 1, wherein the panel 1 may beunaffected by the force applied to the frame 109. In other embodiments,the spacing element 116 b is sufficiently long such that a tip of thespacing element 116 b abuts a surface of the panel 1. This adds furthercontrol of the shape of the plate 2.

In some of the embodiments, the frame assembly 100 comprises a pluralityof spacing elements 116 arranged spaced apart from corners of the frame109. One or several spacing elements 116 may be arranged along eachperimeter or side of the frame 109. If a single spacing element 116 isarranged along each side, it is preferably centered between the cornersof the frame 109.

Each spacing element 116 may comprise a screw with a predefined length.This means that the screw can be fully seated such that the head and tipabut respective surfaces, whereby a predefined curvature of the plate 2is obtained. The level of curvature may be adjusted by one or severalspacers arranged between the head and the surface which the headengages. This is particularly useful if multiple spacing elements 116are arranged along a single side, or if different sides have differentlengths. The more spacers provided, the less force will be applied tothe frame 109. Alternatively, as shown in FIG. 5h , predefined heightdifferences may be generated via other methods, e.g. by milling theframe to the predefined heights, allowing a more continuous supportstructure.

FIGS. 5a-5h illustrate embodiments of an assembly 200, which may becombined with the first frame element 102 described above. Theembodiments shown in FIGS. 5a-5h are shown inverted relative to theembodiments shown previously, with the plate 2 at the top.

As shown in FIGS. 5a and 5b , the frame assembly 200 may comprise afirst frame element 202, and a second frame element 203. The first frameelement 202 and the second frame element 203 may be elongated members,each having a support portion 201 a, 201 b. The first frame element 202and the second frame element 203 may e.g. be L-shaped in cross section.A first portion of each of the first frame element 202 and the secondframe element 203 may be configured to extend along the edge of thepanel 1. A second portion of each of the first frame element 202 and thesecond element 203 forms the support portion 201 a, 201 b, and may beconfigured to extend from the perimeter of the plate 2 a short distance,such as a 1-3 cm, over the surface of the plate 2 when assembled.Furthermore, the second frame element 203 may be arranged on top of thefirst frame element 202 and such that the perimeter of the plate 2 isarranged between the second portion of each of the frame elements 202,203 when assembled. Therefore, each support portion 201 a, 201 b maysupport or engage opposing surfaces of the plate 2, such as isillustrated in FIG. 5 g.

In some embodiments, such as illustrated in FIGS. 5c-5d , a gasket 205(e.g. gaskets 205 a, 205 b, 205 c, 205 d, 205 e) is arranged between thefirst frame element 202 and the second frame element 203. The gasket maye.g. be arranged on the support portion 201 a of the first frame element202. Also, a sealing 204 a may be arranged on the support portion 201 bof the second frame element 203.

The gasket 205 may have a varying thickness along its length, i.e. alsoalong the length of the first frame element 202. This provides forobtaining a desired curved shape of the perimeter of the plate 2 whencaptured between the first frame element 202 and the second frameelement 203, as is illustrated in FIGS. 5f-5g . For example, the gasket205 has opposing ends and may be thinner between the opposing ends thanat said ends. This provides for obtaining a predefined concavity of theperimeter of the plate 2. The gasket is sufficiently stiff that it isthicker at the ends even when compressed. The gasket 205 may be about1.5-2.0 mm at the ends and about 1 mm thinner at the center.

In some embodiments, the gasket 205 has a plurality of sections alongits length. The thickness of each section may vary. For example, a firstsection 205 a of the gasket is provided at one of its ends and a secondsection 205 b of the gasket at the other of its ends. The first section205 a and the second section 205 b may have a first thickness that maybe equal at each section. At least a third section 205 c of the gasketis arranged between the first section 205 a and the second section 205b. The third section 205 c has a second thickness. The first thicknessis thicker than the second thickness. For example, difference inthickness is about 0.5-2 mm, preferably about 1.0 mm. The difference inthickness may vary depending on the length of the gasket 205 and theedge of the plate 2 at which the concavity is to be introduced. In someembodiments, fourth and fifth sections 205 d, 205 e may be providedbetween the first and second sections 205 a, 205 b and the third section205 c, respectively. The fourth and fifth sections 205 d, 205 e may addfurther control of the shape of the concave curve provided by thearrangement 200. The length of each the first and second sections 205 a,205 b may be about 2-20% of the total length of the gasket 205. Thelength of the third section may be about 60-96% of the total length ofthe gasket 205. The length of each of the fourth and fifth sections 205d, 205 e may be about 10-20% of the total length of the gasket 205. Insome embodiments the total length of the fourth and fifth sections 205d, 205 e is shorter than the length of the third section 205 c, and thetotal length of the first and second sections 205 a, 205 a is shorterthan total length of the fourth and fifth sections 205 d, 205 e. Thisprovides for a parabolic concave curve along the length of the frameassembly 200.

A distance between the support portion 201 a of the first frame element202 and the support portion 201 b of the second frame element 203 may bediscontinuous in an assembled state, as can be seen in FIG. 5 e.

In order to maintain the concavity of the plate 2, the first frameelement 202 and the second frame element 203 may be held together suchthat the distance between the support portions 201 a, 201 b ismaintained in the assembled state. The first frame element 202 has afirst hole 217 a and a second hole 217 b arranged at opposing ends ofthe first frame element 202, such as at the second portion of the firstframe element 202. The first and the second hole 217 a, 217 b arearranged in a first plane. A third hole 217 c is arranged between thefirst hole 217 a and the second hole, such as centered between the firsthole 217 a and the second hole 217 b. The third hole 217 c is providedin a plane that is different from the first plane. The distance oroffset between the plane in which the first and second holes 217 a, 217b are arranged and the plane in which the third hole 217 c is arrangedmay be substantially the same as the difference in thickness between thefirst and second sections 205 a, 205 b and the third section 205 c, i.e.about 0.5-2 mm. In some embodiments the first and second holes 217 a,217 b are centered in each of the first and second sections 205 a, 205 bof the gasket 205 along the length of the first frame element 202.

Similarly, the second frame element 203 may comprise a first hole 218 aand a second hole 218 b arranged at opposing ends of the second frameelement 203. A third hole 218 c may be arranged between the first hole218 a and the second hole 218 b of the second frame element 203. Thefirst hole 218 a, the second hole 218 b, and the third hole 218 c of thesecond frame element 203 is generally arranged in the same plane whenthe second frame element 203 is disconnected from the first frameelement 202. The second frame element 203 may be less stiff or weakerthan the first frame element 202 and be deflectable such that each hole218 a, 218 b, 218 c of the second frame element 203 is aligned with theholes 217 a, 217 b, 217 c of first frame element 202. Therefore, thesupport portion 201 b of the second frame element 203 may be deflectedsuch that it extends in plane, which is curved in the assembled state ofthe frame assembly 200. Screws 219 a, 219 b, 219 c may be insertedthrough the aligned holes 217 a, 217 b, 217 c; 218 a, 218 b, 218 c andmay directly engage the panel or engage a threaded hole in the panel 1,which will hold the frame elements 202, 203 in the assembled state.Other relative arrangements of the holes 217 a, 217 b, 217 c; 218 a, 218b, 218 c are foreseen, wherein the center holes 217 c, 218 c of eachframe element 202, 203 are misaligned in the relaxed state of the secondframe element 203 but aligned in the deflected or stressed state of thesecond frame element 203.

In some embodiments, the first frame element 202 forms a frame side, andthe second frame element 203 forms an edge cover. If used together withthe frame 109 discussed with regard to FIGS. 4a-4c , the frame side mayreplace the second frame element of the embodiments of FIGS. 4a-4c .Therefore, the frame side comprises the support portion 201 a with asupport surface generally opposing the frame 109 and is configured tosupport the gasket 205.

As illustrated in FIG. 6, a component (e.g. a sealing component 204 a)may be provided between the support portion 201 a and the plate 2. FIG.6 illustrates the resulting forces and torque generated when a force 220is applied to second frame element 203 a. A second force 221 is appliedto support portion 201. Therefore, a net torque 222 is generated, i.e.counter-clockwise in the illustrated arrangement. The plate 2 willassume a curved path, as is illustrated with dotted line 223.

In an embodiment shown in FIG. 7, an alternative arrangement is providedfor providing curvature of plate 2. In this embodiment, support block301 is arranged to support glass plate 2. Support block 301 has asurface portion comprising a tapered edge 303 at an angle from secondframe element 103A. Plate 2 is pressed against the top surface ofsupport block 301 from pressure 201 b from first frame element 102 andsealing 204 a. Pressure 201 b causes plate 2 to follow the contour ofthe top surface of block 301 and plate 2 is forced into a curving planeat an angle to the plane of second frame element 103A. The resultingpath of plate 2 is shown by curvature path 310. Tapered surface portion303 is angled between 0.5 degrees and 3 degrees from second frameelement 103A.

In an embodiment shown in FIG. 8, a variation of the embodiment shown inFIGS. 5a-5g is provided. In this embodiment, second frame element 203has been modified, such that a portion 410 has been removed from theedge portion 203 c of second frame element 203. This reduces the forcerequired to bend second frame element 203 in a manner that results in acurvature of plate 2. Portion 410 may be removed by a milling process,by a carving or cutting process, or second frame element 203 may beformed without portion 410 via a molding process or similar. Portion 410preferably reduces the depth of second frame element 203 at thenarrowest point by between 5-20%.

The frame elements of the embodiments of the assembly may be made fromsheet metal and given a desired design, thickness, and/or be made fromdifferent materials such that the forces, shapes, torques, etc.discussed above are obtained.

Embodiments comprise a method for assembling the panel 1 and the plate 2for the optical touch sensitive system. The method may compriseproviding the frame elements according to the embodiments presentedherein. The method further comprises attaching the first frame elementto the second frame element, supporting the plate at a support portionof the assembly, and attaching at least one of the first frame assemblyand the second frame assembly to the panel such that the support portionextends in flat or curved plane. Also, the method comprises attachingthe second frame element to the first frame element such that thesupport portion extends at least partially in a second plane generallyopposite at least a portion of the first frame element and is spacedapart from the first plane. A curvature of the first frame element maybe controlled with a spacing element attached to the first frame elementand may thereby tilt the support portion to control a curvature of theplate.

FIG. 9 illustrates a top plan view of an example of a touch-sensitiveapparatus 99. Emitters 30 a are distributed around the periphery oftouch plate 10, to propagating light across touch surface 20. Detectors30 b are distributed around the periphery of touch surface 20, toreceive part of the propagating light. The light from each of emitters30 a will propagate to a number of different detectors 30 b on aplurality of light paths 50.

The embodiments above describe methods of achieving control of plateshape and curvature. The following embodiments describe desirable shapesof the plate for achieving improved performance of a touch sensorsystem. Light paths 50 may conceptually be represented as “detectionlines” that extend across the touch surface 20 between pairs of emitters30 a and detectors 30 b. The emitters 30 a and detectors 30 bcollectively define a grid of detection lines 50 (“detection grid”) onthe touch surface 20, as seen in a top plan view. The spacing ofintersections in the detection grid define the spatial resolution of thetouch-sensitive apparatus 99, i.e. the smallest object that can bedetected on the touch surface 20. The width of the detection line is afunction of the width of the emitters and corresponding detectors. Awide detector detecting light from a wide emitter provides a widedetection line with a broader surface coverage, minimizing the space inbetween detection lines which provide no touch coverage. A disadvantageof broad detection lines may be a reduced ability to differentiatebetween separate objects and a lower signal to noise ratio.

As used herein, the emitters 30 a may be any type of device capable ofemitting radiation in a desired wavelength range, for example a diodelaser, a VCSEL (vertical-cavity surface-emitting laser), an LED(light-emitting diode), an incandescent lamp, a halogen lamp, etc. Theemitters 30 a may also be formed by the end of an optical fiber. Theemitters 30 a may generate light in any wavelength range. The followingexamples presume that the light is generated in the infrared (IR), i.e.at wavelengths above about 750 nm. Analogously, the detectors 30 b maybe any device capable of converting light (in the same wavelength range)into an electrical signal, such as a photo-detector, a CCD device, aCMOS device, etc.

The detectors 30 b collectively provide an output signal, which isreceived and sampled by a signal processor 130. The output signalcontains a number of sub-signals, also denoted “projection signals”,each representing the energy of light received by one of light detectors30 b from one of light emitters 30 a. Depending on implementation, thesignal processor 130 may need to process the output signal forseparation of the individual projection signals. The projection signalsrepresent the received energy, intensity or power of light received bythe detectors 30 b on the individual detection lines 50. Whenever anobject partially or completely occludes detection line 50, the receivedenergy on this detection line is decreased or “attenuated”.

The signal processor 130 may be configured to process the projectionsignals so as to determine a property of the touching objects, such as aposition (e.g. in a x, y coordinate system), a shape, or an area. Thisdetermination may involve a straight-forward triangulation based on theattenuated detection lines, e.g. as disclosed in U.S. Pat. No. 7,432,893and WO2010/015408, or a more advanced processing to recreate adistribution of attenuation values (for simplicity, referred to as an“attenuation pattern”) across the touch surface 20, where eachattenuation value represents a local degree of light attenuation. Theattenuation pattern may be further processed by the signal processor 130or by a separate device (not shown) for determination of a position,shape or area of touching objects. The attenuation pattern may begenerated e.g. by any available algorithm for image reconstruction basedon projection signal values, including tomographic reconstructionmethods such as Filtered Back Projection, FFT-based algorithms, ART(Algebraic Reconstruction Technique), SART (Simultaneous AlgebraicReconstruction Technique), etc. Alternatively, the attenuation patternmay be generated by adapting one or more basis functions and/or bystatistical methods such as Bayesian inversion. Examples of suchreconstruction functions designed for use in touch determination arefound in WO2009/077962, WO2011/049511, WO2011/139213, WO2012/050510, andWO2013/062471, all of which are incorporated herein by reference.

In the illustrated example, the apparatus 99 also includes a controller120 which is connected to selectively control the activation of theemitters 30 a and, possibly, the readout of data from the detectors 30b. Depending on implementation, the emitters 30 a and/or detectors 30 bmay be activated in sequence or concurrently, e.g. as disclosed in U.S.Pat. No. 8,581,884. The signal processor 130 and the controller 120 maybe configured as separate units, or they may be incorporated in a singleunit. One or both of the signal processor 130 and the controller 120 maybe at least partially implemented by software executed by a processingunit 140.

FIG. 10a illustrates a substantially flat rectangular touch plate 10according to the prior art. In this example, the touch plate is made ofglass, plastic, or any other materials such as PMMA (Poly(methylmethacrylate)). Two axes are defined in FIG. 10a . The x-axis is definedas the axis running parallel to and equidistant from the pair of longedges of the rectangle and along the flat surface of the touch surface.The y-axis is defined as the axis running parallel to and equidistantfrom the pair of short edges of the rectangle and along the flat surfaceof the touch surface. At least a portion of the top surface of touchplate 10 comprises touch surface 20.

FIG. 10b illustrates an example of a touch apparatus according to theprior art. FIG. 10b shows the touch apparatus in cross section whereinthe cross section runs along the x-axis of the plate 10. Light isemitted by emitter 30 a, passes through transmissive plate 10 throughtouch surface 20 and is reflected by reflector surface 80 of edgereflector 70 to travel in a plane substantially parallel with touchsurface 20. The light will then continue until deflected by reflectorsurface 80 of the edge reflector 70 at an opposing edge of thetransmissive plate 10, wherein the light will be deflected back downthrough transmissive plate 10 and onto detectors 30 b. Where an objectis applied to touch surface 20, some of the light above the touchsurface 20 is occluded. This occlusion is detected by the touchapparatus and used to determine the presence, size, and/or shape of theobject. The emitters and detectors may be arranged in a number of otherconfigurations such that the light from the emitters is delivered to thetouch surface and delivered from the touch surface to the detectors.Other known arrangements are that of arranging the emitters anddetectors above the touch surface and transmitting and receiving thelight directly without the use of reflecting surfaces. The light mayalso be delivered to the touch surface by means of a wave guide, fiberoptic cable, or other optical component.

FIG. 11a illustrates an embodiment of touch plate 10 similar to thatshown in FIG. 10a but wherein the touch plate 10 is curved. In thisembodiment, the plate remains substantially flat in the direction of they-axis but is curved in a concave direction relative to the x-axis. Inthis embodiment, the x-axis is defined as the axis running parallel toand equidistant from the pair of long edges of the rectangle. The vertexof the parabola or paraboloid of the touch surface is where the touchsurface is deepest relative to the edges of the touch plate. Where thex-axis is positioned at the height of the edge of the touch plate, thecurvature of the plate can be measured using the distance of the touchsurface from the x-axis. FIG. 11b shows a cross-section view along thex-axis of the touch plate 10 of FIG. 11 a.

FIG. 11c shows an example embodiment of a curved touch plate 10. Thetouch plate 10 has a width of 1900 mm along the x-axis and a height of1070 mm along the y-axis. In this example embodiment, the glass isshaped such that the touch surface follows a parabolic curve relative tothe x-axis. The midpoint O of touch surface 20 is the center of thetouch surface and the midpoint of the x-axis. Where the curvature of thetouch surface 20 is parabolic, the maximum distance a between the touchsurface and the x-axis is at the center point O of the touch surface.

FIG. 11d shows the maximum allowed concave distance a and maximumallowed convexity b. The maximum allowed convexity b may be asignificant consideration as a portion of the touch surface that issubstantially convex may result in occlusion of the light between theemitters and detectors and significant loss of touch signal. The maximumallowed convexity b is a negative number in the present examples.

In one embodiment, the range of the distance a for vertically orientatedtouch plate is limited in order to improve the yield and performance oftouch systems. The range is set dependent on the size of the touchsystem. A smallest value is needed to assure that non-parabolicdeviations in the glass shape and convexity in the integration doesn'tresult in a convex integrated touch surface. A largest value is neededin order to assure that the height of the light field for the finaltouch system is kept reasonably low in order to enable better contactdetection and lift-off detection for touch objects. Preferably, range ofthe distance a is 0-2.5 mm.

The maximum distance a is a positive number for a concave glass in thepresent examples. The curvature of the touch surface may therefore bemodelled as:F(x)=−a+cx ²

In the present example embodiment, a maximum distance a between the 1900mm long cross section of the touch surface in FIG. 11c and the x-axis is2.0 mm. Therefore, an ideal parabolic curve for touch surface 20 may be:F(x)=5.5*10⁻⁶ *x ²−2.0

where F(x) is the distance between the x-axis and the touch surface atposition x wherein F (x) is zero at the mid points of the edges. i.e.where the x-axis intersects the perimeter.

FIGS. 12a and 12b illustrates an embodiment of touch plate 10 similar tothat shown in FIG. 11a but wherein the touch plate 10 is curved in twoaxes. FIG. 12a shows a top plan view and FIG. 12b shows an isometricview of touch plate 10. In this embodiment, the plate is curved in aconcave direction relative to the x-axis and is also curved in a concavedirection relative to the y-axis. As with the embodiment shown in FIG.11a , the x-axis is defined as the axis running parallel to andequidistant from the pair of long edges of the rectangle and passingover the center point O on the touch surface. Therefore, the curvatureof the plate can be measured from the distance of the touch surface fromthe x-axis. Similarly, the y-axis is defined as the axis runningparallel to and equidistant from the pair of short edges of therectangle and passing over the center point O on the touch surface.Therefore, the curvature of the plate along this axis can be measuredfrom the distance of the touch surface from the y-axis.

FIGS. 12c and 12d shows respective section views along the x-axis andy-axis of the touch plate 10 of FIGS. 12a and 12b . In an exampleembodiment of a curved touch plate 10. The touch plate 10 has a width of1900 mm along the x-axis and a height of 1070 mm along the y-axis. Inthis example embodiment, the glass is shaped such that the touch surfacefollows a parabolic curve relative to the x-axis. The center point O oftouch surface 10 is the center of the touch surface and parallel withmidpoint of the x-axis. Where the curvature of the touch surface 10 isparabolic, the maximum distance a between the touch surface and thex-axis is at the center point O. The maximum distance a is a positivenumber for a concave glass in the present examples. The curvature of thetouch surface may therefore be modelled as:z(x,y)=−a+b*x ² +c*x ² y ² +d*y ²

where z is the distance between the plane defined by the x-axis andy-axis and the touch surface, and x and y are co-ordinates in the planeof the glass.

In an example embodiment having a flat perimeter around the plate with amax distance of 2.0 mm measured along the x-direction for y=0 (i.e.middle of plate):z(x,y)=−2+5.56e−06*x ²−4.74e−11*x ² y2+1.7e−05*y ²

In another example embodiment having a concave perimeter around theplate with a max distance of 2.0 mm measured along the x-direction fory=0 (mid short to short of screen) and with a max distance of 1.5 mmmeasured along the y-direction for x=0 (mid long to long of screen).Where the top and bottom edges have 1.0 mm max distance and the left andright edges have 0.5 mm max distance:z(x,y)=−2.5+5.56e−06*x ²−2.37e−11*x ² *y ²+1.28e−05*y ²

FIG. 13a shows a section view along the x-axis of light propagatingacross an example embodiment of a curved touch plate 10 touch surfacehaving a curved profile in the x-axis. In the section view, thepropagation paths of light from a point light source 1310 are shown.Dotted lines 1320 show propagation paths of light emitted from pointlight source 1310 a that are not received by detector surface 1340.Solid lines 1330 show propagation paths of light emitted form pointlight source 1310 that are received by detector surface 1340. As shownin the figure, a portion of the light is lost above the detector, aportion is lost below the detector, and a portion of the light isreceived at the detector surface. A person looking from the emitterpoint towards the mirror image of the detector (mirrored in the touchsurface) will perceive the detector size as 2.2 times larger than thereal detector. This magnification effect is an effect of using an offaxis parabolic mirror. In the specific case of touch systems, thisresults in a detection signal boost of a factor of 2.2, when comparingto a flat touch surface. This boost applies only to the signal and notsignificantly to the ambient light otherwise received by the detectors.In a preferred embodiment, the detectors and emitters of the touchsystem are 3 mm or less above the touch surface (either directly orindirectly) and the length of the detection lines being in the rangefrom 100 to 2500 mm, the angle of incidence is extremely close to 90degrees. With this, gracing incidence, dirt or anti-glare coatings onthe touch surface have no practical impact of the reflection, so it ispractically a mirror.

FIG. 13b provides a graph of the angle of the emitted light from thepoint light source 1310 with respect to the z-coordinate of the lightpath at the edge of the model of FIG. 13a . The detector surfacez-coordinate range is shown by the vertical axis. Light emitted by pointlight source 1310 received at a z-coordinate within that range isreceived by the detector.

FIG. 14a shows a section view of the embodiment of FIG. 13a . In thesection view, the propagation paths of light from a second point lightsource 1410 are shown. In this example, the detection signal boost isapproximately 3.3. FIG. 14b shows the corresponding graph of FIG. 13bfor the second point light source 1410.

FIG. 15a shows a section view of the embodiment of FIG. 13a . In thesection view, the propagation paths of light from a third point lightsource 1510 are shown. FIG. 15b shows the corresponding graph of FIG.13b for the third point light source 1510. In this example, thedetection signal boost is approximately 3.03.

FIG. 16a shows a section view of the embodiment of FIG. 13a . In thesection view, the propagation paths of light from a fourth point lightsource 1610 are shown. FIG. 16b shows the corresponding graph of FIG.13b for the fourth point light source 1610. In this example, thedetection signal boost is approximately 2.71.

FIG. 17a shows a section view of the embodiment of FIG. 13a . In thesection view, the propagation paths of light from a fifth point lightsource 1710 are shown. FIG. 17b shows the corresponding graph of FIG.13b for the fifth point light source 1710. In this example, thedetection signal boost is approximately 2.19.

FIGS. 13a-17b demonstrate that different emitter positions utilizedifferent parts of the touch surface. The parts of the touch surfacethat work as reflectors will depend on the actual shape of the glass andthe placement and sizes of the emitter and detector apertures surface1340.

However, the touch plate 10 cannot be manufactured, positioned, or heldin shape perfectly. Consequently, a certain amount of deviation can beexpected between the curve followed by the touch surface and an idealparabolic curve.

FIG. 18a shows a graph of a mathematically defined parabolic curve and areal-world parabolic touch surface. In the example embodiment of FIG.18a , a curved touch plate 10 has a width of 1900 mm along the x-axisand a height of 1070 mm along the y-axis (wherein the x-axis and y-axisare defined as in the embodiment shown in FIG. 12a,4b ). In this exampleembodiment, the glass is shaped such that the touch surface followsparabolic curve 1810 relative to the x-axis. The maximum distance abetween the touch surface and the x-axis is 10 mm. The mathematicallydefined parabolic curve is defined as 1820. The graph shows thedeviation between the mathematically defined parabolic curve representedby dotted line 1820 and real touch surface 1810. Here, the real touchsurface is asymmetrically warped. FIG. 10b shows the short to short midcross section of a 2180 mm diagonal, 16:9 ratio, thermally temperedglass that is just within or at the maximum limit of concave distance <6mm as well as |parabolic deviation|<0.5 mm.

The parabolic fit of the touch surface 1810 has an s-shaped residual.Such asymmetrical warping may be the result of problems with transportrollers or an uneven temperature distribution during the rapid coolingphase of tempering process during manufacture.

FIG. 18b shows a graph of the deviation between the mathematicallydefined parabolic curve and a real-world parabolic touch surface of FIG.18 a.

The following table defines a preferred set of restrictions on the shapeof the touch surface in order to achieve an optimal touch surface shape.The term ‘warp’ defines the distance of the touch surface from therespective axis intersecting the center point O in the direction of thez-axis.

Min Max Min Max Max Max x-axis x-axis y-axis y-axis con- parabolic Glasswarp warp warp warp vexity* deviation size (mm) (mm) (mm) (mm) (mm) (mm)55″ 1.0 3.50 0.0 1.35 0.1 0.5 65″ 1.0 4.50 0.0 1.65 0.1 0.5 70″ 1.0 5.100.0 1.85 0.1 0.5 75″ 1.0 5.70 0.0 2.00 0.1 0.5 84″- 1.0 6.00 0.0 2.000.1 0.5 86″

Convexity b is shown in FIG. 18a . Parabolic deviation is shown in FIG.18 b.

FIG. 19a shows another graph of a mathematically defined parabolic curveand a similar glass to that of FIG. 18a but wherein the glass of FIG.19a is out of range and not recommended for touch system production. Onereason for the large concavity shown in FIG. 19a may be that thetempering process has been run with too large differences between bottomand top cooling parameters in a quenching process during manufacturing.The mathematically defined parabolic curve is defined as 1920. The graphshows the deviation between the mathematically defined parabolic curveand real touch surface 1910.

FIG. 19b shows a graph of the deviation between the mathematicallydefined parabolic curve and a real-world parabolic touch surface of FIG.19a . The real-world parabolic touch surface of FIG. 19a is an exampleof a symmetrical but higher order warping (e.g. W shaped). Such warpingmay significantly reduce signal boost and may be caused by symmetricaltemperature problems (e.g. too hot in center or edge of glass) duringthe manufacturing tempering process.

FIG. 20a shows an embodiment in which the touch surface forms aparaboloid. In FIG. 20a , a top plan view of the touch surface is shownwith contour lines showing the depth of the touch surface relative to aflat plane intersecting the four corners of the touch surface. Thenumbers shown on each contour represents the depth of the contour. Thex-axis, y-axis, and diagonal-axis d are all shown. The x-axis is definedas an axis running parallel to and equidistant from the pair of longedges of the rectangle. The y-axis is defined as an axis runningparallel to and equidistant from the pair of short edges of therectangle. Diagonal-axis d is defined as an axis running diagonally fromone corner to a diagonally opposite corner. In this embodiment, thex-axis, y-axis, and diagonal axis d of touch surface 10 each describe aparabola with respect to the depth of the touch surface. In FIG. 20b ,diagonal-axis d is shown running from the bottom left corner to the topright corner. In the example embodiment of FIG. 20a , the curved touchplate 10 has a width of 1900 mm along the x-axis and a height of 1070 mmalong the y-axis.

FIGS. 20b-20d show optional parabola configurations for the embodimentshown in FIG. 20a . FIG. 20b shows a graph of the desired parabola ofthe touch surface underneath the x-axis and relative to the x-axis. Thedeviation (bottom axis) from the x-axis is shown relative to theposition (left axis) along the x-axis. FIG. 20c shows a graph of thedesired parabola of the touch surface underneath the y-axis and relativeto the y-axis. The deviation (bottom axis) from the x-axis is shownrelative to the position (left axis) along the y-axis. FIG. 20d shows agraph of the desired parabola of the touch surface underneath thediagonal-axis and relative to the diagonal-axis. The deviation (bottomaxis) from the x-axis is shown relative to the position (left axis)along the diagonal-axis.

The embodiments shown in FIG. 20a-20d describe a touch surface providingsubstantial signal boost for signals travelling between most emittersand detectors. However, the non-flat perimeter of the touch surfacemakes manufacture and assembly of such a system more complex.

FIG. 21a shows an embodiment in which the touch surface forms analternative paraboloid to that of the embodiment shown in FIG. 20a . Aswith FIG. 20a , FIG. 21a provides a top plan view of the touch surfaceis shown with contour lines showing the depth of the touch surfacerelative to a flat plane intersecting the four edges of the touchsurface 10. The numbers shown on each contour represents the depth ofthe contour. X-axis, y-axis, and diagonal-axis d are all shown. Thex-axis is defined as an axis running parallel to and equidistant fromthe pair of long edges of the rectangle. In this embodiment, the x-axisof touch surface 10 describes a parabola with respect to the depth ofthe touch surface. The y-axis is defined as an axis running parallel toand equidistant from the pair of short edges of the rectangle. In thisembodiment, the y-axis of touch surface 10 also describes a parabolawith respect to the depth of the touch surface. Diagonal-axis d isdefined as an axis running diagonally from one corner to a diagonallyopposite corner. In FIG. 21b , diagonal-axis d is shown running from thebottom left corner to the top right corner. In the example embodiment ofFIG. 21a , the curved touch plate 10 has a width of 1900 mm along thex-axis and a height of 1070 mm along the y-axis. The perimeter of thetouch surface of this embodiment is flat or close to flat. Inembodiments where the perimeter of the touch surface is flat or close toflat, the surface beneath some detection lines will not be perfectparabolas. Even for an almost perfect integrated glass shape with a warpin the range of 1-2.5 mm some detection lines (a very small portion)will actually have less signal than for a flat glass. This smalldrawback is counter balanced by the significant overall signalimprovements. Furthermore, touch systems where the perimeter of thetouch surface is flat or close to flat can be easier to manufacture andassemble.

FIG. 21b shows a graph of the desired parabola of the touch surfaceunderneath the x-axis and relative to the x-axis. The deviation (bottomaxis) from the x-axis is shown relative to the position (left axis)along the x-axis. FIG. 21c shows a graph of the desired parabola of thetouch surface underneath the y-axis and relative to the y-axis. Thedeviation (bottom axis) from the x-axis is shown relative to theposition (left axis) along the y-axis. FIG. 21d shows a graph of thedesired parabola of the touch surface underneath the diagonal-axis andrelative to the diagonal-axis. The deviation (bottom axis) from thex-axis is shown relative to the position (left axis) along thediagonal-axis.

As will be apparent, the features and attributes of the specificembodiments disclosed above may be combined in different ways to formadditional embodiments, all of which fall within the scope of thepresent disclosure.

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements and/orstates. Thus, such conditional language is not generally intended toimply that features, elements and/or states are in any way required forone or more embodiments or that one or more embodiments necessarilyinclude logic for deciding, with or without author input or prompting,whether these features, elements and/or states are included or are to beperformed in any particular embodiment.

The present invention has been described above with reference tospecific embodiments. However, other embodiments than the abovedescribed are equally possible within the scope of the invention.Different method steps than those described above may be provided withinthe scope of the invention. The different features and steps of theinvention may be combined in other combinations than those described.The scope of the invention is only limited by the appended patentclaims.

What is claimed is:
 1. A touch sensing apparatus having a long edge anda short edge, the apparatus comprising: a display panel; a frameassembly configured to support the display panel, the frame assemblycomprising a plurality of frame elements, said plurality of frameelements comprising: a first frame element configured to surround aperimeter of a back surface of the display panel; a second frame elementconfigured to connect with the first frame element to form a bracket,the second frame element including a support portion having a first sidefacing the first frame element, said support portion configured tosupport the display panel; and a plate configured to attach with asecond side that is opposite the first side of the support portion, theplate including a touch surface opposite the second side, the touchsurface including: a center point; a first edge and a second edgeparallel to the short edge; and a third edge and a fourth edge parallelto the long edge; wherein a first plane defined by the touch surface iscurved with respect to a second plane defined by the short edge and thelong edge; wherein a distance between a first line in the first planethat passes through the center point and the second plane variesaccording to a parabolic function.
 2. The touch sensing apparatus ofclaim 1, the apparatus further comprising: at least one emitter arrangedaround at least one of the first, second, third, and fourth edges of thetouch surface, wherein the at least one emitter is configured to emit atleast one beam of light to propagate across the touch surface; at leastone detector arranged around at least one of the first, second, third,and fourth edges of the touch surface, wherein the at least one detectoris configured to receive at least one beam of light from the at leastone emitter; and a processing element configured to determine, based onoutput signals of the at least one detector, a position of an objectadjacent to the touch surface.
 3. The touch sensing apparatus of claim1, wherein the support portion of the second frame element comprises agasket.
 4. The apparatus of claim 3, wherein the gasket is configured tohave varying thickness along at least one length of the gasket such thatthe gasket forms a curved shape.
 5. The touch sensing apparatus of claim1 wherein the support portion of the second frame element comprises atleast one support block with at least one tapered edge.
 6. The apparatusof claim 1, wherein the support portion of the second frame element iscurved.
 7. The apparatus of claim 1, wherein the touch surface compriseglass or plastic.
 8. The apparatus of claim 1, wherein the touch surfaceis flat prior to installation and an application of a force from one ormore of the plurality of frame elements is configured to change acurvature of the touch surface.
 9. The apparatus of claim 1, wherein thetouch surface is curved before installation into the frame assembly. 10.A touch sensing apparatus having a long edge and a short edge, theapparatus comprising: a display panel; a plate including a touchsurface; and a frame assembly comprising a plurality of frame elementsconfigured to support the display panel and the plate; said the touchsurface including: a center point; a first edge and a second edgeparallel to the short edge; and a third edge and a fourth edge parallelto the long edge; wherein a first plane defined by the touch surface iscurved with respect to a second plane defined by the short edge and thelong edge; and wherein a distance between a first line in the firstplane that passes through the center point and the second plane variesaccording to a parabolic function.